Do Dual Coils Affect TC Accuracy?
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I would theorize that cooling is faster with dual coils due to the increased volume of cooling liquid in contact with the material. One coil of .1 would have half the wick of two .05 coils.
Was given, as a bonus, by my b&m, when i bought my TFV4 Mini, both the single and dual build decks. You can garauntee that the dual deck will never see daylight as i only use tc these days and the reasons you list above are exactly why it will never see daylight, i like stress free kiss vaping
Plus its another assumption in vaping, dual coils must be better....
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I think I figured it out!
If not, then this is at least some brilliant folly.
Coils in parallel, being resistors, will still be seen by an ohm meter (the mod) as a single resistor. To keep the math simple, let's assume they are perfectly identical, 1-ohm coils.
Two 1-ohm coils in parallel create the equivalent of a .5-ohm resistor.
Let's assume they heat and cool mathematically perfect, in perfect unison, and therefore this "variable" resistor (controlled by its temperature) is easier to discuss.
We now have "one" resistor for the mod to analyze hundreds of times a second, as it does. It's looking for a change in resistance.
That change has to be expressed in milliohms, or some such finite unit of granularity. It's looking for so many units of change per unit of time.
A Heating Cycle:
Each increased milliohm that a single, serial wire would report back, is now taking twice the milliohms (for each coil independently) for the circuit as a whole to report back as 1 milliohm of change.
Not a problem for the mod, it will happily push more wattage at it until the heat increases enough in both coils to increase the ohms enough to meet the TCR's delta enough to decide it's reached the target temperature.
A Cooling Cycle:
I think this is where the "magic" happens (the magic of dual coils being anemic).
The power is cut (or reduced) and waiting for the milliohms to drop sufficiently so that it can kick in again.
But just as before, it takes 2 milliohms of change in each coil, to produce 1 milliohm of change for the circuit as a whole.
Since the cooling is a "static" function of the thermodynamics of the coil mass and surface area (and wick), it doesn't have the benefit of a mod to push more cooling at it. It just has to cool at its own natural rate.
The cooling that happens on each coil, independently, is identical in behavior to its single coil counterpart; even when each coil, of a dual, has more wraps, they don't work to retain the heat more, due to the topology of a spiral, spaced coil.
So the cooling cycle is nearly identical between the single build and dual build, but the dual build is required to cool longer, a full 2 milliohms drop in resistance worth of cooling, longer, to report back only 1 milliohm worth of cooling as the mod sees it.
I believe it's this extended cooling cycle, repeated over and over (perhaps dozens or even hundreds of times a second) that results in a net cooler temperature, as compared to the ohm-unhampered single coil build.
The single coil, reports "I'm cooler now," faster.
The dual coil reports "I'm cooler now," slower and therefore, in fact is cooler than the single coil would be, at that reporting.
I like that you want apply some thought to the situation, i read this as no problem heating dual coils as they are effectively combined during the heating phase as its electro mechanical, but the cooling cycle on each coil is open to more factors that expose it to parameters that can be highly individualised...and cause delays before the coils are ready to be reliably read and heated again....
Or in other words, in the time it took me to read that, and write my reply i could have drained my tank, washed it out, wrapped and wicked a single coil, reassembled the tank and filled it and been on my way, which is probably what i would have preferred to have done rather than talking about or thinking about dual coils
Im a kiss vaper. Single wire, single coil. Problems go bye byes. One thing im finding on here is that a lot of people seem to have more time than i do to fiddle
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Each individual coil will have a different delta rise and fall compared to the unit as a whole but the TFR would be the same.
So if the unit as a whole was dropping 1 milliohm a microsecond per degree each individual coil would be dropping 2 milliohms a microsecond per degree.
I was thinking this, too, but if you think about the topology, geometry of a spaced coil, each wrap is less affected by the whole, in therms of the distribution of its thermal mass.
I suggest we can think of a small, arbitrary segment of it, as being the representative of the whole, in terms of its cooling profile, as a whole.
I've noticed this too when dry firing coils. When looking at a wide coil (many wraps) cooling, compared to a short coil at the same gauge cooling, they both cool at about the same rate.
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Do we at least agree that two 1-ohm resistors in parallel read as .5-ohms by an ohm meter (a mod)?
And that if the combined resistors heated up such that they read as 1.5 ohms, that each resistor would have to be 3 ohms (and therefore as hot as 3 ohms)?
And that the reverse of that, as it cools, is also true?
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Jesus, theres some proper thinking and theorising going on here!
I failed basic maths, so im out of the numbers side of things
Anyone else not that cluey want to join me by sitting back, shutting up and sharing some popcorn? (i have salted or non-salted)
I failed basic maths, so im out of the numbers side of things
Anyone else not that cluey want to join me by sitting back, shutting up and sharing some popcorn? (i have salted or non-salted)
Yes to the first sentence. No to the rest.
Remember, doesn't matter if it's two pieces (or twenty, or two hundred), when in parallel, it's still ONE resistor, and the actual resistance is...the actual resistance. The temp coefficient of resistance for the material still applies, and is measured in exactly the same manner. Those two example coils in parallel did halve the resistance, but they're also splitting the current between them in the process (which is WHY the resistance is halved), so follow that to the logical conclusion.
This is a lot of overthinking to solve what essentially boils down to a "you're doing it wrong" issue when it comes to problems with dual coils and temp control. If you have a weak vape with a dual coil build, there's something wrong with the build (or the mod or the atomizer) that's effecting the results, and not simply because it's dual coils. Sure, single coil builds tend to be less problematic to get working properly, but everything in your OP you attribute to dual coils can and does happen to people building singles for temp control as well, and for the same reasons.
Yes, exactly.
As for the different rise and fall between the two imperfect resistors, that's a detail that is overshadowed by the halving of the combined, read ohms (or nearly halving, because they're not perfect).
E.g.,
Two 1-ohm resistors gives us .5-ohm.
While a 1.1-ohm resistor and .8-ohm resistor gives us .463-ohms.
So, the effect is close enough that an overarching behavior can be pointed to.
So, like, im gonna just keep building my singlies because everyone in this thread made my head hurt
And i ran out of popcorn
So we agree that two 1-ohm resistors at room temp are halved to .5-ohms, but don't agree that when they're heated to a temp such that they each reach 3-ohms, they'd be read as halved (1.5 ohms) by the mod?
How could this not be true?
I think for the discussion to progress in a meaningful way we need to agree on at least this important point, or explain to me why it's not the case.
But that's determined by a different set of rules, when looked at under the hood, than its single resistor counterpart.
E.g.,
The single resistor at 2 ohms only has to drop .5 ohms to get to 1.5 ohms.
The dual parallel resistor at 2 ohms must have each of its two resistors, drop a full 1 ohm to get to 1.5 ohms.
If we're talking about the cooling cycle, this is almost twice as long (not quite due to the math involved with heat dissipation, but close enough to point to an effect).
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Why twice as long? The dual-coil setup has twice the surface area and wicking as the single coil.
The "anemic vaper syndrome", within the realms of math & physics, points to a physical problem with the atomizer or build, not an inherent issue.
I think because the geometry of a spiral coil of thin-ish wire, tends to defeat heat dissipation across its length. The placement, location, spacing, topology of that "twice the surface area," most of its mass is in a disadvantaged location, compared to a block of metal, or even a sheet.
I think it's like when you take a blowtorch to a length of wire, the whole wire doesn't heat evenly. You get a really hot spot where the flame is and a heat gradient on either side. The cooling potential of the neighboring parts of the wire, in any given section, is not so good.
So the overwhelming requirement of each coil needing to be twice the ohms (and the mostly linear heat that equates to), trumps any small cooling effect of coil mass dissipating heat from "way over there," so to speak.
So every part of the coil has to be twice as hot, but we don't have twice the cooling (as it relates to duration).
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I already explained it. They aren't faking being half the resistance, it's not an arbitrary notion, once in parallel two identical coils ARE half the resistance, and it's ONE circuit. The mod is not applying power to two coils and then dividing the resistance to arrive at a figure, it's applying power to one circuit and reading the actual resistance. You need to grasp this, because it's where your theory fails.
The thermodynamics of varying coil masses doesn't matter either, because the TCR for the material doesn't change. X resistance delta for Y material always equals Z temperature, if it's a single wrap on a single coil, or 100 wraps on 10 coils.
What you're missing here is that a dual coil is a single resistor, not two. In your example, put together two 1 ohm coils and they read as .5. It's a .5 resistor. It climbs to 1.5 ohms, not two times 3 ohm. The difference is (if we're dealing with the same gauge wire) that it has more mass and will therefore need more power to heat up and more time to cool down (most likely). But it's a single .5 ohm resistor for all intents and purposes.
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Oh, and regarding heat flux as we discussed earlier. While a dual coil will require double the power in theory, it's not quite so in practice. There's limited space in an atty so the heat will be more concentrated, plus the vapor production is considerably increased. In my experience, in a real world situation, 1.5 times the watts is more accurate. Also, something like a Clapton dual coil might require more than double the power than a single wire single coil, it's due to the significant increase in coil mass to heat up.
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You're acknowledging there are two resistors and that it reads as one at "rest" (it's never really resting because of room temp fluctuations, but if that helps to visualize it). We agree. So take that a step further and agree that the physics of those laws don't mystically change as it heats and cools.
If you were to read the ohms on each resistor independently, while it was heating and cooling, It still has to follow the math of the resistors in parallel.
That means for every one ohm of resistance change the single circuit reports, two ohms of resistance must change in each separate coil of the circuit.
The math doesn't change just because interesting stuff is happening to the coils.
I am absolutely acknowledging it's read as a single resistor.
Back to your example: It can't climb to 1.5 ohms unless each resistor inside it, climbs to 3 ohms.
Are we really not agreeing on this point?
By what sorcery are those two resistors exempt from following Ohm's Law? They don't even know about the "single" resistor they're a part of. Know what I'm sayin'.
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